Consequences of Substitution in the Photoelectron Spectra of [2, 2]Paracyclophanes: Separation of ‘through-space’ and ‘through-bond’ interactions as a consequence of fluorosubstitution
✍ Scribed by Edgar Heilbronner; John P. Maier
- Publisher
- John Wiley and Sons
- Year
- 1974
- Tongue
- German
- Weight
- 467 KB
- Volume
- 57
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
Abstract
The PE. spectra of [2, 2]paracyclophane (1), 4‐amino[2, 2]paracyclophane (2) and 1, 1, 2, 2, 9, 9, 10, 10‐octafluoro[2, 2]paracyclophane (3) are presented. The bands corresponding to ejection of the photoelectron from the five highest occupied π‐orbitals have been assigned. The ‘observed’ orbital energies (i.e. the negative ionization potentials) are discussed in terms of ‘through space’ and ‘through‐bond’ interactions between the semi‐localized π‐orbitals (e~1g~) of the benzene moieties and the C, C‐σ‐orbitals of the ethylene bridges.
The PE. spectrum of 3 shows that the fluorine‐induced lowering of the C, C‐σ‐orbital energy effectively ‘turns‐off’ the ‘through‐bond’ interaction. The resulting pattern of the first four bands confirms the assignment given for 1.
Finally the band shifts induced by an amino group in position 4 are again in agreement with this assignment. Attention is drawn to the phenomenon of ‘orbital switching’ as a consequence of substitution in loosely coupled systems such as 1.